The invention relates to an apparatus for the enrichment of the mixture supplied to an internal combustion engine by a fuel injection system. The fuel injection system includes an electronic monostable multivibrator which delivers fuel injection control pulses whose length depends on the aspirated air quantity and the engine rpm. The apparatus includes a constant current source which charges a capacitor linearly and determines the magnitude of an adjustable supplementary current which can be admitted to the fuel injection controller for prolonging the duration of fuel injection.
It is known that just after starting, and in some cases during starting, an internal combustion engine, for example an Otto engine, requires a somewhat enriched fuel-air mixture to insure smooth running.
It is generally intended that this enrichment be gradually reduced to zero during a predetermined amount of time. It is known to employ a circuit which delivers a useable output potential which changes linearly, for example to the negative supply voltage. This known circuit includes a capacitor connected in a Darlington-like circuit of two transistors in which, after the capacitor has almost completely discharged due to the starting process, a gradual charging takes place which produces a desired potential shift at one of the electrodes of the capacitor. The capacitor and its associated transistors are connected in a so-called Miller integrator. In this known circuit, after the starting process is terminated, the linear potential decrease is initiated and terminated after a predetermined time. However, in this known circuit, it is not possible to account for any possible special requirements of the engine, for example the engine temperature, the rpm or the load factor. However a truly optimum adaptation of the mixture, during the start or post-start operation, requires a very sensitive adaptation which must take into account the prevailing engine conditions.